Dec., 1919
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C A E M I S T R Y
with moistened furnace magnesite. At the temperature of the furnace in which they are used, the steel container melts back for a distance of one or two inches from the exposed surface and impregnates the dead burned magnesitc which it encloses. The suriace thus becomes prrretically jointless. Because of this monolithic surface and the somewhat more w e n texture of this construction. the spalling tendency is considerably less than that of magnesia or silica brick. The stiffening effect of that part of the metal case which does not luse also helps reduce spalling to a minimum. This brick is iiscd in the back walls, bulk heads, and gas ports of basic open-hearth furnaces and in the side willls ai electric steel-melting furnaces. An installatian of these brick in a &ton Heroult furnace is shown in Pig. 5 .
1149
operation, thc mccssity for greater efficiency from refractories is forced upon us. This improvement in refractories can only bc accomplished by the coiiperation oi the consumer and the producer. The consumer should be familiar with the conditions prevailing in his furnaces, such as temperature, slag, gases, dust. mechanical wear, abrasion, expansion and contraction, etc., M that he is in position t o know what the brick must stand.
Fro.
I--S)dll~z. PORIIONos .DISINTSGRA-IED Reanacroav B R ~ C ASTBB Z 5 YBnns' .'HRYICB IN BLISFFUINAEB I ZNING. Nom S I M Z L A 011~ ~ Y C n l C g S IN SSN,' POPTlON 1RrJ IN UN"S*Pl nnrcL7
On the other hand, thhmanufacturer of refractories should know the limitations and possibilities of his product. He should know the effect on quality in service produced by variation in moisture, 6neiiess of griud, proportionate sizing of particles, method of molding, drying, and burning. Such information enables him to advise the consumer as to the kind of brick best suited for his particular needs
OP rCzx.iTo~ rmc FOWACR SHOWZNDPA^ BNI M B T & ~ ~ ~MACNBSITS sB Baicx SZDB WALL.LIN~NU
FEGJ-VIEIY
In addition t o the physical and chemical properties of reiiactoiies the design of the shape used also is worthy of careful atteot;on. Difficult and intricate shapes should be awrded as much as possible. They cannot be repressed, are more liable to defects in workmanship, and cost more. With few exceptions they cannot be used t o advantage over the standard sizes and shapes. Standard sizes are carried in stork by the refractories manuiacttmrs and ordinarily are available t o the user promptly when needed. Eccause of the time required for manulacture, a number of weeks must necessady elapse before special shapes can be secured XIR~ZSON-WILBBR RBI.P.AC~ORIHS COXPANY P I T T S B U W B , PGNNSYLYINII
INTERESTING FACTS CONCERNING REFRACTORIES IN THE IRON AND STEEL INDUSTRY By C E. NBYBITT AND M I ,. BBLL
In the manuiacture oi iron and steel the part played by refractories is a most important one and up to the present time has not had proper mnsideration. Owing t o inneased production, larger and more complicated furnaces. and economy of
Fzo Z-CLAY BmcR mox C 0 m . B ~ z . s MAIII'OII ~ BLASTFurnrcg SnowZAG EROSION PRoDuCBD BY DUSTC ~ a a m m o BLAST
In the iron and steel industry the temperature range is wide Temperatures in the intenor of a blast furnace vary from 260' C a t the top to 1 8 0 0 ~C. a t the tnybes. Refining temperatures are high in open-hearth, Bessemer converters, and electric furnaces, while temperatures m quenching and annealing iumaces aze moderate. Besides this wide range of temperature, refractories must meet a wide variation en physical requirements, such as wrrosivc action of acid, basic or neutral slags, sudden thermal changes, load, abrasion, impact, and expansion. Early in OUT investigation we found need forsimple tests which would give us some data on the important qualities necessary refractory brick. These tests should be easily and rapidly ex-
.
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T E E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
ecuted to be able to be run in quantity and should show a close relation to actual service conditions. This means that the tests employed must be shorter and more severe than actual working conditions and must show variation in working quality.
Vol.
II,
No.
12
by heat are serious factors In the table below are shown results of tests on good commercial silica brick crushed a t room temperature atid a t 1350" C., together with bricks defective because of fire cracks, poor moulding, poor slicking, etc.
LE
OPBN.H&ARI~Foarr~csSnowrwo FAZLVEE DUB
Mncnrtie m pounds per square inch
STRBNCTA-OLSBN CB
Bdek
At 1350' C 989 1123 1152 1282
A series of tests was developed for b Data obtained irom thcse tests, after showed that the most important working qualities could be determined by two 01 three tests, namely, the spalling and hot crushing tests for silica brick, and the spalling, hot load. and slagging tests for clay brick. We do not deem it necessary a t this time to give these methods in detail as they have been published in some of our former papers.' By the use of these tests we are trying to solve some of the refractory problems in OUT industry, a few of which are the following: Why does the life of blast-furnace linings vary from 2 to 7 years, basic open-hearth roofs from 2 5 t o 400 heats. soaking pits from G to 18 months, converter bottoms from 4 t o 16 heats, and ladle linings from 4 t o 2s heats? How can we explain a blast-furnace lining bricks and in anothcr rick will be surrounded
Pia. 4-Si~lcn
1300
__
1169
A t 1350'
C
437 466
466 498
657 505
cause a decided shorleuing ofthe life of a uch as an open-hearth roof where there are ges. This is well illustrated when commercial ud without fire cracks arc subjected t o our
Baicss DBYRCTiYB PROM Fral C s r c x s , Puox Sucxmo. AND
Bonaron MATSRIILS
by a number of sound bricks? These and many other problems present themselves which are difficult t o solve. Variations in quality of the refractories are due to method used in grinding, moulding, setting, drying, burning, and cooling. It is a wellknown fact that silica bricks show a idling OR of approximately 50 t o Go per cent in mushing strength when heated from room temperature to r350* C., hence defectswhichlower themechanical streneth - of a Droduct which has already been weakened
* Tronr. Am. Soc.for Tssitng Molcrtds, 1910, 1917, 1918, 1SlS.
Fm. 6 SPIILLINO OP CLAYBBLCK IN Roos OP ~
Am F a ~ ~ n c n
Roofs of go-ton open-hcarth furnaces working under normal conditions with producer gas should !ast for an average of z m heats. Bricks taken from a furnace roof after 261 heats showed an average spalling loss of zo per cent. Another roof which made 2 2 I heats showed a loss of 3 . 2 per cent. In a similar roof in which the life was only 80 beats the average spatling loss was 47 per cent. The degree of fineness or size of particles especially in silica brick has a very pronounced effect on the spalling loss. The
Dec., 19x9
T E E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C E E M I S T R Y
1rgr
into a fire-clay bridi heated t o 1350' C. by applying a load of 16wlbs. Results are depth of penetration expressed in inches. -Maehine-Med0.27 0.46
-Hand-Mad0.72
0.29
0.55
0.41
The degree of fineness t o which the raw material is ground in d a y brick produces results similar to those of silica brick, namely, the finer the grind, the greater the spailing loss. The results given here are the averages obtained from two brands of clay brick, onc of coarse grind and the otlier of finc grind. Loss by Smiling Coarse Grind.. .......................... Fine Grind ..............................
Per cent 8.47 49.95
Rcduction in strength by heating is shown by the impact test, A steel ball approximately zi/slbs. in weight was dropped by a suitably designed machine from successive increasing heights of 2 in. upoii the heated brick. The brick tested was a wellknown ladle hrick ma& largely of plastic clay. Hsifrrr OP F ~ L OP L BGL IO Teniperntttrc............... 30" c. Average height. inches.. 51 . 2
....
Fit;. 7 - W i a ~ nIN Am Fuxlrnc~PRODUCBLI I.AY'IUI.Y
BY
Si.** A-ON
AND
TBMPFRATrrRB C B A N O B S
finer the grind the higher the loss, which in turn means a decided shortening of the life of the structure when subjected to severe thermal changes as illustrated in this table. FINSNBSS OF GRLNDZNE Mesh 4 8 12
SP*'rnO
LOSS
Per Cent 30.4 47.6 63.2
The interesting facts stated above in regard to silica brick are generally true with clay brick, except that they are not so marked, owing to the fact that the raw materials have entirely different properties. However, the method of manufacture has D pronounced effect on the qualitics of clay brick. This is illustrated by the average spalling valuc of sin different brands of brick,
BBEAKBBIC= 340' c. 4800 c. 40.3 33.6
Thc effect of extreme variation in degree of burn is well illustrated in a recent shipment of clay checker brick. The average spalling loss was r q per rent for the avuage burn and 60 per cenr for the hard-burned bricks. From all the comparative data it,is evident that refractories require. more than general consideration. They demand a most thorough study by both producer and consumer. Investigators should try t o adopt simple practical tests whicir can be mn ih quantity and which give data showing variations in quality, which reflect in the life of the structure. The consumer judges his refractories by the life obtained and demands a product giving a more uniform life. Variations in uniformity are largely due t o methods of manufacture. It is believed that a much more uniform product can be secured if a careful study is made of the variationsin manufacture whichaffect the important qualities.
sr€%x.
CdnNBGIL? CCmP*NY P I r n m J R C A , P*N)ISY'"ANI*
SUPERIOR REFRACTORIES By ROSSC . PDRDY
There is a demand for better quality in refractories, the real urgency and volume of which are growing apace with the rapid development in more eficicnt manufacturing equipment. The most vital limiting factor in the development and a d a p t a t i k of electric furnaces is adequate refractories, thc present furnaces having many compromises in design and operation, and serious limitation in use because of failure of the refractories to withstand the service conditions that otherwise would be placed upon them. New inventions of processes to lessen cost, improve quality, recover by-products, eliminate material losses, etc., etc., are not war babies, but the natural result of actual necessity for new and greater refinement in materials and economics in processes. The increase in mechanical and dielectric strains on high tension insulators resulting from extensive development of electric power, the increased strain on spark plugs and the increase in hazards due t o failure of spark PLO.8 B r o c ~ s C u r ~ TII-OSIMILARSILIC~ ~oa S S A P ~ SSBOWIYE V A X I A T ~ N plugs in air craft are but two of many examples of the inm Fsr~irmss01,G m m creasing urgencies that can be met only by materials that necessitate more intense heat treatment. Examples of inthree of which are machine-made, but by different processes, creases in demand for improved quality and refinement are while three are hand-made brick. more nufae~ousand perhaps mare urgent for metals than for AYBKACE PBRCENTACB Loss BY SPALLLINO AT 1350' C. ceramic ware. YMecbiaeMade-Hand-MadNew alloys that require higher temperatures for tempering. 26.9 11.7 9.4 7.3 3.4 16.7 new glasses that necessitate mare intense heat treatment t o Again this variation in quality of refractories is shown by the melt and refine, new labor-saving devices that entail more results obtained from the load test in which a steel ball is pressed severe temperature changes, new by-prcducts that must be
